Meerkats

Some assumptions in science can be rethought after new discoveries are made.

Take the "altruistic" behaviour among meerkats, for instance.

As it has been found out, the individual which acts as a sentinel for the group also obtains many advantages from its "altruism". It can be the first to eat, before standing guard while the others also eat. When it sees a predator approaching the group, the sentinel is the first to seek shelter, so it's lees exposed to danger. Besides, after the sentinel meerkat issues an alarm, the others gather or move away, thus attracting the attention of the predator on them rather than on the sentinel.

Also among humans, "altruistic" acts often give a reward to those who behave this way. Those who done a kidney to a relative or a stranger, for instance, receive appreciation and gratitude, and such nonmaterial rewards can be very relevant to some people.